1. Field of the Invention
The present invention relates to circulators and, more specifically, to features in the housing which alters the magnetic bias in the ferrite media of the circulator and prevent the formation of higher order modes.
2. Description of the Related Art
RF/microwave circulators often exhibit higher order modes similar to what can occur in waveguides. Stripline circulators are often in circular housings exhibiting similar modes as a circular waveguide. Prior art solutions to prevent these modes include changing the dimensions of both the housing and the ferrite pucks within the housings. However, for size constrained designs this is not an option and, in particular, for wide bandwidth (>10%) it can be difficult to find dimensions that avoid all possible modes that can be excited in the frequency band of interest. Another prior art solution to prevent/eliminate mode is to use an absorptive material placed such as to absorb the field associated with mode(s) while having minimal impact on the fundamental. However, using absorber materials adds cost both for the material itself and for the added assembly steps required to install it. Additionally, using absorber materials does not always stop the undesired mode from forming, but rather dissipates it which add loss to the fundamental frequency. Accordingly, there is a need in the art for a solution that prevents the formation of the undesired higher order modes in resonance stripline circulators and isolators.